Progression from Step 2 (single dose) to Step 3 (paired doses) was based on each participant's increase in RCVL following their first dose of 400 mg VOR (Visit 3), compared to that measured at baseline (Visit 2). Progression from Step 3 (paired doses) to Step 4 (multiple doses) will be based on each participant's increase in RCVL following the 2nd in a paired dose VOR 400 mg (total doses = 3, Visit 6), compared to that measured at baseline (Visit 2).